Polycarbonate resins are widely used in electrical, mechanical, automotive and medical applications because they have excellent transparency, heat resistance and mechanical strength. In recent years, a resin composition having a titanium dioxide pigment filled in a polycarbonate resin and having excellent light reflectivity has been proposed. Molded articles prepared from this resin composition are used for a reflector for a backlight of a liquid crystal display, a reflector for an illuminating push switch or optoelectronic switch, a display inner frame of a vending machine, a stroboscopic reflector, and the like.
This resin composition is required to have excellent light reflectivity, a high degree of whiteness and excellent color. Further, along with a reduction in the thickness and size of molded article, the resin composition is required to have thermal stability which enables it to endure high-speed and high-temperature injection molding. That is, it is required to have no yellowing and silver streaks which are caused by thermal degradation at the time of molding. The yellowing degrades light reflectivity, and it is assumed that the silver streaks do not exist on molded articles in the first place. Further, resin compositions used for light reflectors are often required to have flame retardancy. In this case, it is often required not to use a bromine flame retardant and a phosphorus flame retardant so as to reduce environmental burdens.
Various proposals have been made to improve the thermal stability and flame retardancy of a resin composition containing a titanium dioxide pigment. For example, Patent Literature 1 proposes coating the surface of a titanium dioxide pigment for a polymer composition with aluminum oxide and organosiloxane to prevent yellowing of the titanium dioxide pigment. Patent Literature 2 proposes adding a titanium dioxide pigment surface-treated with aluminum oxide to a polycarbonate resin to improve the surface appearance and coatability of the resin composition. Patent Literature 3 proposes adding polyorgano hydrogen siloxane to improve the thermal stability of a resin composition comprising an aromatic polycarbonate resin and a titanium dioxide pigment. Patent Literature 4 proposes a resin composition which comprises an aromatic polycarbonate resin, a titanium dioxide pigment containing a specific amount of aluminum oxide and a metal salt and has excellent light reflectivity and heat resistance. Patent Literature 5 proposes a light reflector which comprises a polycarbonate resin, an alkali metal salt of perfluoroalkane sulfonic acid and a titanium dioxide pigment and has excellent heat resistance and total light reflectance. Patent Literature 6 proposes a resin composition which comprises an aromatic polycarbonate resin, a glass filler, titanium oxide and organic sulfonic acid and has excellent flame retardancy, strength and rigidity. Patent Literature 7 proposes a resin composition which comprises an aromatic polycarbonate resin, titanium oxide, silica, polyorganosiloxane and polytetrafluoroethylene, is suitable for a reflector and has excellent flame retardancy. Patent Literature 8 proposes a resin composition which comprises an aromatic polycarbonate resin, other thermoplastic resin, titanium oxide, a metal salt and a fluoropolymer and has excellent flame retardancy and impact resistance.    (Patent Literature 1) JP-B 60-3430    (Patent Literature 2) JP-A 11-60743    (Patent Literature 3) JP-B 63-26140    (Patent Literature 4) JP-A 2003-183491    (Patent Literature 5) JP-A 2002-372609    (Patent Literature 6) JP-A 2003-226805    (Patent Literature 7) JP-A 2003-213114    (Patent Literature 8) JP-A 2003-342462